Strength of a riveted lap joint (working-stress method): The safe (governing) strength of a riveted lap joint is taken as which of the following?
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AShearing strength of the rivets
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BBearing strength of the plates or rivets
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CTearing (net-section) strength of the plate
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DLeast of (a), (b), and (c)
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EGreatest of (a), (b), and (c)
Answer
Correct Answer: Least of (a), (b), and (c)
Explanation
Introduction / Context:Riveted joints can fail in multiple modes. A safe design recognizes the weakest (governing) mode under the applied load and limits the joint capacity accordingly.
Given Data / Assumptions:
- Lap joint with standard rivets and plates.
- Working-stress design framework.
Concept / Approach:The joint fails if any of its critical capacities is exceeded. Three primary capacities are checked: (1) shear of rivets, (2) bearing of rivet/plate, and (3) tearing of the plate across the net section. The safe joint strength is the smallest (least) of these capacities because that mode will govern first.
Step-by-Step Solution:
Compute rivet shear capacity based on number of shear planes.Compute bearing capacity using permissible bearing stress and plate (or rivet) thickness.Compute plate net-section capacity using net width and permissible tensile stress.Adopt the least value as the joint strength.Verification / Alternative check:Compare efficiencies of the joint (joint strength divided by member strength) to ensure acceptable performance.
Why Other Options Are Wrong:Selecting any single mode (shear or bearing or tearing) ignores other potential lower capacities; picking the greatest would be unsafe.
Common Pitfalls:Using gross rather than net section in tearing checks; forgetting double shear in cover-plate joints; miscounting effective rivets.
Final Answer:Least of (a), (b), and (c)